This invention relates to food packaging film and food storage bags made from said film for storing, for example, produce such as vegetables and fruits. More particularly, this invention relates to flexible produce storage bags having a pattern of microholes specifically designed to allow produce contained in the bag to breathe in a controlled rate, such that localized condensation is reduced, which in turn, reduces microbial (bacteria and mold) growth and produce mushiness (softness). The perforated bags of the present invention also control the weight loss of the stored produce, thus minimizing the shriveling and wilting of unpackaged products.
Because fresh fruits and vegetables give off gases and retain moisture when stored in bags, it has long been a challenge for the packaging industry to provide a container or bag for storing produce that will help maintain the quality or shelf life of the produce while stored.
There are several well-known techniques available for packaging of produce to maintain their quality or extend their shelf life, including, for example, the use of controlled modified atmosphere packaging, shrink wraps, functional or active packaging and impermeable plastic storage bags. However, such known procedures do not adequately control or maintain the quality of produce. There is still a need in the industry for a packaging material such as a storage bag that will minimize local condensation and produce weight loss.
In an attempt to address the condensation problem of stored produce, U.S. Pat. No. 4,735,308 discloses an internally lined food storage bag useful in the storage of moisture-retentive foods, such as fruit and vegetables. The storage bag comprises a hand-closed water-impermeable outer bag containing an absorbent inner bag. The construction of the bag described in U.S. Pat. No. 4,735,308 is complicated and does not involve the use of microperforations to control the perspiration of produce.
It is also known to provide a ventilated plastic bag, for example, a bag containing slits as described in U.S. Pat. No. 3,399,822 or bags with microperforations as described in U.S. Pat. No. 4,886,37, for storing vegetables. U.S. Pat. No. 3,399,822, for example, provides slits in a plastic bag to prevent contamination of vegetables stored in the bag, but does not address the moisture or weight loss problem of stored vegetables.
U.S. Pat. No. 4,886,372, for example, discloses controlling the ripening of produce and fruits by using a container or bag having a selected size and number of openings therein. However, the holes of the bags of U.S. Pat. No. 4,886,372 are too large, for example, from 20 mm to 60 mm, for adequate control of the weight loss of the produce. The prior art also describes bags having microholes which are too small or too many and are not suitable for storing small quantities of produce for in-home consumer use.
In view of the deficiencies of the prior art, it is desired to provide a film and food storage bag with microperforations of a size and number which maintains the quality of produce and reduces the problems associated with produce packaged in a prior art ventilated bag, in a totally sealed impermeable package or in a control/modified atmosphere package.